We have traced the origin and growth of philosophical opinions,
outlined the development of schools and systems of philosophy, and
indicated what seemed in each case to be an advance in or a
retrogression of philosophic thought. There remains the task of
inquiring into the general laws in obedience to which philosophy took
in the course of its development the particular direction which it has
taken.

That at one time rather than at another, in one place rather than in
another, men should appear whose lives and thoughts had a decisive
influence on the course of the development of philosophy, that
countless factors, hereditary, temperamental, educational, and so
forth, should result in determining the philosophical career of such
men, -- these are phenomena the origin of which lies beyond the scope
of the philosophy of history; they are data, which must be
considered as given by experience, in much the same way as the innate
tendency to vary is taken as a datum by the biologist, who
restricts his investigation to answering the question, How is this
tendency affected by
environment? The task of the philosophy of history is merely to
inquire how such data were influenced by social, political, religious,
and other influences. Starting, therefore, with the unexplained
appearance of Plato, Aristotle, St. Augustine, St. Thomas, Descartes,
Spinoza, how may we formulate the laws according to which these and
other contributors to the development of philosophic thought were
influenced by the internal and external conditions which, combined with
the personal factor commonly called genius, produced the changes and
vicissitudes of the history of philosophy?

The laws of historical development are a posteriori laws. They
are not to be deduced from a priori principles, but built up by
a process of inductive reasoning from the study of the facts of
history. This does not mean that history is the resultant of forces
acting capriciously, but that the forces which produce historical
development -- being dependent on physical conditions, mental
temperament, and the action and interaction of social institutions,
customs, and organizations -- are contingent, not necessary causes;
that consequently the philosophy of history is not a geometry of the
evolution and play of such forces; and that the laws which it seeks to
establish are not deductions from definitions and axioms, but
generalizations, similar to the post facta generalizations of
the statistician. Divine Providence and human reason are the two great
factors which determine the course of history. Sometimes these two work
in unison, sometimes they clash; and the result is progress or
deterioration. Wars, revolutions, conquests, educational reforms,
industrial reconstructions, are all the work of man's mind, directed
but not coerced by Divine Providence. Now, Divine Providence works
through secondary causes, and will, which is the motive power of mind,
though free, is not capricious, but follows certain ascertainable laws
in its efforts to advance to a higher social state. The ground of
historical development is, therefore, reason; not pure reason, deducing
events as the logical mind deduces categories, but reason rendered
contingent by freedom, and always subject to the unreasoning opposition
of passion and impulse. Consequently, the laws of historical
development are not a priori principles, as they should be if
the ground of history were pure reason, nor are they mere aggregations
of facts, as they should be if the ground of history were blind force.
They are a posteriori inductions, based on observations, neither
purely logical nor biological, but psychological.

The laws of historical development are organic laws; that is to say,
they deal with vital phenomena. Now, organic laws differ from
mechanical laws in this, that, while the latter may be expressed with
quantitative accuracy, the former can lay claim to qualitative
definiteness merely. In physics, chemistry, astronomy, and geology,
the amount of force expended can be calculated and expressed in terms
of some unit of measurement, and the verification of the laws of these
sciences includes the establishment of a quantitative equivalence
between the force expended and the work accomplished. But when once we
cross the threshold of the biological sciences we must be content with
the formulation of laws which are definite in every respect save that
of quantity. [1] When, therefore, the laws of historical development
formulate the relations between cause and effect they do not pretend to
specify the definite amount of action and reaction.

Another peculiarity of the laws of historical development results from
what is commonly called the continuity of history. This is based
on a quality common to all manifestations of vital activity, namely,
the absolute indelibleness of an effect once produced on the living
organism. "It is the peculiarity of living things," writes Clifford,
"not merely that they change under the influence of surrounding
circumstances, but that any change which takes place in them is not
lost but retained, and, as it
were, built into the organism to serve as the foundation for future
actions. If you cause any distortion in the growth of a tree and make
it crooked, whatever you may do afterwards to make the tree straight,
the mark of your distortion is there it is absolutely indelible; it has
become part of the tree's nature. . . . No one can tell by examining a
piece of gold how often it has been melted and cooled in geologic ages,
by changes of the earth's crust, or even in the last year by the hand
of man. Any one who cuts down an oak can tell by the rings in its trunk
how many times winter has frozen it into widowhood, and summer has
warmed it into life. A living being must always contain within itself
the history not merely of its own existence but of all its
ancestors." [2] This peculiarity of living organisms, which may be
likened to the vis inertiae of physical force, appears in
aggregate life as the continuity of history, and conditions the
development of philosophy as well as that of every other vital product.

[2] Lectures and Essays (London, 1886), p. 54.

The philosophy of the history of philosophy is, therefore, the
study of the organic laws in obedience to which philosophy took the
particular course which it did take in its historical development. Some
of these laws we have already observed as occasion offered; we have
observed, for example, that a period of national enthusiasm and
national prosperity is usually one of great activity, and in particular
of great constructive activity, in philosophy; we have observed that
the era of introspective philosophy corresponds with the period of
mental maturity of a nation. Similarly, laws may be formulated
expressive of the influence which climate, racial characteristics,
literature, art, religion, etc., exercise on philosophy. Or, again,
laws may be formulated in reference to conditions which are internal to
philosophy itself, as for example that psychology is first dogmatic and
afterwards critical, or that a system of ethics is determined by the
psychology of the author or the school. We are not,
however, concerned here with such particular laws, but rather with the
general formula under which all the particular laws, external and
internal, of the history of philosophy may be subsumed.

Such a general formula is development. In the course of its
history, philosophy has passed from a relatively simple to a relatively
complex condition, from a homogeneous to a heterogeneous state, from
indeterminateness to determinateness. But what are the characters of
this development? A glance at the succession of philosophical systems
will convince us that the evolution of philosophy has not followed
"an increasing purpose"; philosophy has not always and everywhere
passed from less to greater perfection; it has not gathered momentum as
it came down the ages; truth has not come down to us gaining power and
volume in its course, like the avalanche in its descent from the
mountain top. If philosophy were the gradual unfolding of an idea, if
that idea were the only reality, and if its evolution were consequently
monistic, the progress of philosophy should have been "a triumphal
march from victory to victory, through province after province of newly
acquired truth, without a single reverse, without ever retreating from
territory once fairly won." Such, we know, has not been the history of
the philosophical sciences: the development of philosophy has followed
a more complicated course than that of continued increase in
perfection.

Comte, it will be remembered, distinguished three stages in the
development of human thought; namely, the theological, the
metaphysical, and the positive, or scientific. This generalization is
one-sided; it judges all thought from the view point of positivistic
prepossessions. Besides, it is inaccurate; for there have been
alternations of the metaphysical and the scientific periods in
philosophy. The age of Plato was metaphysical, that of Archimedes,
Euclid, and Ptolemy was scientific; the thirteenth century returned to
metaphysics, the sixteenth was preŽminently a scientific century,
while the nineteenth went back to metaphysics
in the form of transcendentalism. Still less accurate is Cousin's
generalization, according to which philosophy has passed successively
through the stages of sensism, idealism, scepticism, mysticism, and
eclecticism. According to Hegel, philosophy has, in the course of its
development, assumed different forms, each of which it successively
transcends, thus gaining a fuller, richer, and more concrete content,
so that the progress of philosophy corresponds to the development of
the logical categories, Being (Eleatics), Becoming
(Heraclitus), Individuality (Atomists), etc. No one will,
however, maintain that Hegel's generalization meets with more than an
approximate verification from the study of the facts of history.

We shall be content here with describing the development of philosophy
in general terms as a process of alternate progress and retrogression,
-- a vast connected growth from lower to higher, with alternating
periods of stagnation or degeneracy. This alternation of progress and
retrogression is a characteristic of all development. Even in the
evolutionary hypothesis the survival of the fittest does not
necessarily mean the survival of the best. Indeed, rhythm is a quality
of all motion whatsoever: in the physical, in the physiological, in the
psychological, as well as in the social order, progress is essentially
conditioned by periodicity. As in the individual life, so in the
aggregate life, there is a fluctuation of vitality, a rise and fall.
The line which represents human progress in industry, in art, in
literature, and in philosophy is not an ascending vertical, nor a
straight line ascending obliquely from the horizontal, but an
undulating curve, like the record of the pulsation, now rising above
the horizontal, now falling below it, representing at different points
the same height of perfection or the same depth of degeneracy, but
never representing exactly the same condition of human progress. The
motion of the rowboat floating with the tide, rising and falling with
each successive wave, yet constantly moving forward, so that while it
often rises to the same height, it never rises
twice to the same point of space, is an image of the progress of human
thought, human customs, and even human fashions, which are constantly
changing and constantly returning to previous conditions, without ever
completing the circle of regression. The continuity of life demands
that each successive moment in life recapitulate the entire past.
Eadem sed aliter!

If we are to reduce to general terms the forces which combine to cause
this progress and retrogression of philosophic thought, we shall find
that on the side of progress are the power of Him Who wishes all men to
come to a knowledge of the truth, the attractiveness of truth itself,
the impetus given to philosophic speculation by a Plato, an Aristotle,
an Aquinas, and the enthusiasm of their followers; while opposed to
progress are the necessity of daily toil, the commercial spirit, greed,
unworthy ambition, war, cruelty, despotism, superstition, conservatism,
fanaticism, love of novelty, loyalty to tradition, and intellectual
sloth. Through these agencies does Divine Providence work out its
designs, by these conditions is human reason aided or hindered in its
effort to arrive at a knowledge of the ultimate nature of things, and
by these factors are the rise and fall of philosophy determined. From
Thales to Aristotle there is one great wave of progress which, though
ruffled by petty wavelets of less successful movements, moves onward
until, contemporaneously with the downfall of Greece's political
independence, it begins to sink to the calm level of indifference to
speculative effort. The wave of progress next appears in the doctrines
of the Alexandrian school; it differs in aspect from the wave which
preceded it, -- is less compact in form and more easily broken. In the
early centuries of the Christian era the philosophical movement gathers
strength once more, and rises to its greatest height in the thirteenth
century, after which conservatism, indifference, and sloth play the
part of retrograding forces, until with the opening of the modern era
another movement begins. This movement has continued with alternating
rise and fall until our own day. It has risen at those points where men
like Descartes, Spinoza, Leibniz, Kant, and Hegel have appeared; it has
fallen wherever adverse influences have predominated; but never has it
risen to the altitude attained by that wave of human thought whose
crest touched heaven itself, when reason and faith were united in one
system of knowledge. Whither will this movement bear us? It will carry
us forward, -- we cannot resist the progress of historical development,
-- but will it raise us to a height as great as that to which the past
attained? All will depend on the principles on which philosophical
speculation in the future will rest.

It has been well said that a cripple on the right road will reach his
destination sooner than the swiftest runner who has started in the
wrong direction. Philosophy to-day realizes more than ever the
importance of a right start and a correct method. If, therefore, much
of recent speculation has made a wrong start, the sooner we return to
the principles of former and more successfully constructed systems,
principles often harshly expressed, yet plainly pointing towards the
truth, the sooner will a genuine reform of philosophic method be
possible. The fullest appreciation of the past is compatible with the
most complete originality. To modern philosophers the challenge has ere
now been addressed: "Ye have removed our landmarks; give us others that
are better. . . . Ye have taken away our foothold; what have ye surer
and safer in its place?" The present has much to learn from the past.
If it is vain to strive to stem the progress of the world, it is
equally vain to neglect the study of the past and to spend one's time
in gloomily forecasting the future. The principles which the past has
bequeathed to us should be adapted to the requirements of the future,
and the motto by which all enlightened advancement should be guided is,
Vetera novis augere et perficere.